High tension electric insulator and method of attaching a metal fitting thereto



Patented Mar. 3, 1942 HIGH TENSION ELECTRIC INSULATOR AND METHOD OF ATTACHING A METAL FIT- TING IHERETO Laurence J. Dykstra and Edwin M. Meyer, Rochester, N. Y., asslgn'ors to Victor Insulators, Inc., Victor, N. Y., a corporation of New York Application September 17, 1940, Serial No. %7,162

16 Claims.

This invention relates to a high tension electric insulator and method of attaching ametal fltting thereto, and has for its object to afford a practica and economicai procedure for eflfecting a bond between a silica-containing insulator body,` such as porcelain, and a metal fltting such as a surrounding steel ring adapted to be Secured to a structure where the insulator is to be used.

More particularly,` the invention is intended to aflord a stronger and more durable bond between metal and silica-containing surfaces than has heretofore been commercialiy practicable, and a joint between such parts which constitutes a tight and effective hermetic seal against any'cold or hot liquid or gaseous medium.

A more. specific purpose of the invention isto provide means for firmly uniting asteel or similar 'metal ring to a cylindrical hollow porcelain insulator body such as employed for condenser and pothead bushings where .a conductor extends through the porcelain unit, and a liquid-tight joint between the metal ring and porcelain unit is required.

To these and other ends, the invention consists in the construction and method that will appear clearly from the following description when read in conjunction with the accompanying drawing, the novel features being pointed out in the claims following the specificatio'n.

The drawing is a sectional view of an insulator,

bodiment of the invention.

Referring more particularly to the drawing, I

designates a hollow, generally cylindrical insuconstructed in accordance with a preferred emthe latter from the porcelain shoulder and prevent direct contact, which might result in tracturing the porcelain upon expansion or contraction of the parts.

To attach a ring to a porcelain body in this fashion, the insulator or porcelain body, either with or without the usual silicate glaze covering it, is first fired, or subjected to the usual heat treatments necessary to finish a porcelain insulator; such a fired insulator, after having cooled to normalroom temperature, is placed in a furnace in the position shown, with the metal ring 2 resting upon the asbestos spacing element 1, and heated preferably over a period of about four hours to 1250 F. to 1300 F., such gradua increase in temperature protecting the porcelain against damage from too sudden application of excessive heat, or. the porcelain may be heated to a Iesser degree, but sufciently to eliminate thermal shock when molten antimony is brought into contact with it.

When the porcelain reaches a proper temperature, molten antimony, previously melted in any suitable manner, is poured between the ring 2 and the porcelain, as indicated at 5, and the parts, with the antimony filling the space between the metal ring and the porcelain, are permitted to remain in the furnace for approximately !rom torty-five minutes to one hour and a quarter, the heating process being carried on in a reducing atmosphere, as by charging the furnace with charcoal, in order to prevent oxidation y of the antimony. The antimony may be introbond. 5 designates a body of antimony between the porcelain surface and the interior of` the metal ring, the antimony acting to cause the latter to adhere tightly to theporcelain by forming an alloy with the silica in the insulator body as well as the metal ring, and efiecting a liquidtight joint therebetween.

In the structure shown.. 6 designate a series *of annular ribs or projecting portions, the uppermost one .terminating 'in a shoulder upon.

which an asbestos gasket 1 is placed during the attachingof the metal ring, in order to space duced between the ring and porcelain in powdered or lump form, and the entire assembly, including the porcelain, ring, and antimony, raised to therequired temperature at the same time.

The antimony thus remains in a metallic state, being protected against oxidation, and there is probably formen an alloy of silica and antimony, dueto softening of the silica in the porcelain or the silicate glaze thereon. Whatever the action between the antimony and silica, there is formed an intimate and strong mech'anical bond between the metal ring and the porcelain that effectually prevents separationof these parts,

and serves as a perfect seal against the passage through the joint o'f either hot or cold liquid or gas. This 'is particularly essential where such a bushing is employed with a condenser, cable terminal, pothead, or capacitor that is filled with hot oil which is under pressure, and.it is necessary to prevent leakage of such hot oil between the ring 3 and the insulator body. It will be ing molten antimony between the fitting and the insulator body while maintaining the insulator body at the temperature of the molten antimony,

i approximately from 1250 F. to 1300 F.

bond between a silica-containing surface and a' metal fltting than with any known cements or adhesives that depend upon cohesion between rough surraces for their union, and'it has been determined by actual tests that with a joint such as described, the porcelain will fract'ure before separating rrom the antimony bond. While it is not known with certainty what action takes place, it is believed that the antimony forms an alloy with both the metal ring and the porcelain body, flowing into and intermingling intimately with said surraces so that there is a mechanical overlapping and molecular bond between the antimony layer and both the porcelain and metal surfaces,-resulting in an integral union as-distinguished from a mere cementing together of two opposed surfaces.

While the invention has been described with reference to a particular type of insulaton it is not conflned to this form only, but may b'e otherwise utilized wherever it is desirable to unite a metal fixture to a silica-containing insulator body. and both the structure and method may be modified without departing from the essential features of the invention and the scope of the following claims.

We claim:

1. In a high tension electric insulator, the combination with a silica-containing body, of a metal fltting, and an integral molecular bond of' antimony uniting the metal' fltting and the silica 9. The method of attaching a metal fitting to a porcelain insulator body which consists in first flring the .insulator body and then applying molten antimony between the fitting and the insulator body while maintaining the insulator body at the temperature of the molten antimony,

approximately rrom 1250 F. to 1300 F.

10., The method of attaching a metal fitting to a porcelain insulator body having a silicate ;glaze which consists in first flring the glazed porcelain body and *then applying molten antimony between the fltting and the insulator body while maintaining the insulator body at the tem perature of the molten antimony, approximately from 1250 F. to 1300 F.

uniting the metal fitting and the porcelain body.

3. In a high tension electric insulator, the combination with a porcelain body having a silicate giaze, of a metal fitting, and an integral molecular .bond of antimony uniting the metal fitting and glazed porcelain body.

4. In a high tension electric insulator, the combination with a silica-containing body, of a metal ring surrounding the silica-containing body, and an ,integral molecular bond of antimony between the ring and silica-containing body. g

5. In a high tension electric insulator, the combination with a porcelain body, of a metal ring surrounding the porcelain body, and an integral molecular bond of antimony between the ring I and porcelain body.

of antimony between the ring and glazed porcelain body.

7. In a high tension electric insulator, the combination with a porcelain body, of a metal fitting,

11. The method of attaching a metal ring to body in spaced relation thereto, and applying molten antimony between the ring and the insulator body while' maintaining the insulator body at the temperature of the molten antimony, approximately from 1250 F. to 1300 F.

12. The method of attaching a metal ring to a porcelain insulator body which consists in first firing the porcelain insulator body, positioning the ring around the insulator body in spaced relation thereto, and applying molten antimony between the ring and the insulator body while maintaining the insulator body at the temperature of the molten antimony, approximately from 1250 F. to 1300 F.

13. The method of attaching a metal ring to a porcelain insulator body having a silicategiaze which consists in first firing the giazed insulator body, 'positionin'g the ring around -the insulator body in spaced relation thereto, and applying molten antimony between the ring and the insulator body while maintaining the insulator 'body atthe temperature of the molten antimony, approximately from 1250 F. to 1300 F.

14. The method of attaching a metal fl'tting to a silica-containing insulator body which consists in first flring the 'insulator body, and arranging molten antimony between the metal fitting and the insulator body while heating the insulator to the melting point of the antimony, approximately from 1250 F. to 1300 F.

15. The methodof attaching a metal ring to a silica-containing insulator body which consists in first flring the insulator body, positioning the ring around the insulator body in spaced relation thereto, and arranging molten antimony between the metal ring and the insulator body while heating the porcelain to the melting point of the antimony, approxima ely from 1250 F. to 1300 F.'

and an alloy of silica and antimony constituting an integral molecular bond between the metal flttin'g and porcelain body.

8. The method of attaching a metal tltting to a silica-containing insulator body which consists in first flring the insulator body, and then apply- 16. The meth j of attaching a metal ring to a porcelain insulator body having a silicate g'laze which consists in first firing the glazedinsulator body, positioning the ring around the insulator body in spaced relation thereto, and arranging "molten antimony between the metal ring and the insulator body while heating the porcelain to the melting point o! the antimony, approximately from 1250 F.. to 1300 F LAURENCE J. DYKSTRA. 

